1. Field of the Invention
The present invention relates generally to underwater mapping apparatus and method and more particularly to a subbottom rock mapping probe for measuring the thickness of a sediment layer located on the bottom of a body of water.
2. Description of the Prior Art
Presently, in deeper waters sonic subbottom profiling methods are utilized to obtain an indication of the location of the bedrock surface. In an attempt to verify and correlate the information collected by these methods, core samplings are made. However, core sampling operations experience limitations in penetration and sample losses which result all too often in inadequate or inaccurate information. In addition, the resolution of data collected from sonic subbottom profiling methods is such that an accurate value for the depth to the bedrock is not obtainable.
In shallower waters, such as the surf zone, the effect of the entrained air in the water on the accuracy of the data obtained from sonic subbottom profiling methods is not known. Also, the presence of sand in this region makes it difficult for sonic signals to penetrate to the seafloor and provide accurate data on the rock surface. In addition, sonic equipment is difficult to use in this zone.